Various designs of roller blind systems for vehicles are known. German Published Patent Application 197 39 919, for example, discloses a roller blind system in which a coiling body is mounted at an edge of an opening in a vehicle roof. The roller blind may be withdrawn from the coiling body so that the roller blind extends across the area of the opening to constitute a sunshade in this area. The roller blind is laterally guided by a pair of guide rails into which the longitudinal edges of the roller blind are inserted when the blind is withdrawn from the coiling body.
The disadvantage of this structure is that the forces for actuating the roller blind rise super-proportionally when the blind is withdrawn from the coiling body. First, there is in fact an increase in a retracting force that is exerted on the coiling body by a retracting spring. Additionally, a frictional force is produced by friction between the edges of the roller blind and the guide rails and increases as the withdrawal length of the roller blind increases.
One object of the invention to further develop a roller blind of the type mentioned above that reduces the increase in the actuating forces as an increasing amount of the roller blind is withdrawn.